Experimentally based modelling of failure mechanisms of high-strength concrete under multi-axial loading - MABET

迄今为止，三维加载混凝土结构的失效模拟仍是一个挑战。现有的材料模型通常是由模型参数定义的，这些参数是不可物理测量的量。通常，它们只能通过对已知测试结果的数学校准来确定。因此，现有材料模型的应用往往局限于已知实验的重新计算。特别是对于三维材料模型的情况，应力和应变对各方向力学性能的相互影响被忽略或在很大程度上被简化。由于缺乏实验数据，无法建立新的三维演化规律，因此本研究拟建立一种新的材料模型，并通过实验验证其有效性。适用于高强混凝土结构在多轴荷载作用下的破坏模拟。本文提出了一种新的测量技术，并将其应用于多轴变形状态的实验研究。新型光纤传感器的连续应变测量将提供混凝土试件内部应变分布的新信息。因此，将有可能重新评估混凝土的中观和宏观模型的现有知识。新的材料模型将能够以正确的物理方式描述混凝土在空间加载下的结构行为、损伤状态和破坏机理。该模型将提供未来扩展的能力，以考虑疲劳失效。申请人的初步工作表明，材料定律的基于应变或能量的公式能够定义演化定律和失效表面，其主要由物理可测量的参数定义。随后在有限元程序中实现材料模型将能够在三维应力下对真实的结构进行失效模拟。大量的实际应用，如高强度混凝土中集中荷载的锚固或海上风力涡轮机中的灌浆接缝，都揭示了对此类模型的需求。柏林工业大学的研究小组专注于理论建模，德累斯顿工业大学的研究小组专注于实验研究，这两个研究小组之间的合作开辟了高度的协同潜力。

Failure simulations of thee-dimensionally loaded concrete structures are challenging till this date. Existing material models are often defined by model parameters which are no physically measurable quantities. Often, they can only be determined by mathematical calibration to known test results. Therefore, the application of existing material models is often limited to the recalculation of known experiments. Especially for the case of three-dimensional material models, the mutual influence of stresses and strains on the mechanical properties of all directions is neglected or simplified to a large extend. Additional experimental information is usually missing for the formulation of new three-dimensional evolution laws.A new material model is to be developed and validated experimentally in the present project. It will be suitable for failure simulations of high-strength concrete structures under multiaxial loading. A new measurement technique will be applied and tested for the experimental study of multiaxial deformation states. Continuous strain measurements with a new type of fiber optical sensors will provide new information on the strain distribution in the interior of concrete specimens. Thus, a re-assessment of the current knowledge on meso- and macro-models for concrete will become possible. The new material model will be able to describe the structural behavior, the state of damage and the failure mechanisms of thee-dimensionally loaded concrete in a correct physical manner. The model will provide the capability of a future extension to account for fatigue failure. Preliminary work of the applicants indicates that a strain or energy based formulation of the material law enables the definition of evolution laws and failure surfaces, which are mainly defined by physically measurable parameters. The subsequent implementation of the material model in a finite element program will enable a failure simulation of real structures under three-dimensional stresses. Numerous practical applications, such as the anchorage of concentrated loads in high-strength concrete or the grouted joints in offshore wind turbines, reveal the demand for such models.The cooperation between the research groups of the Technische Universität Berlin, with a focus on theoretical modeling, and Technische Universität Dresden, with a focus on experimental research, opens up a high synergy potential.